The present invention generally relates to drill bits for boring subterranean and sub sea formations. More particularly, the present invention relates to a lubricating nutating single cone drill bit having an axis of rotation skewed relative to the central axis of the bit body in the borehole providing low torque and allowing high compressive loading on the bit assembly.
A number of single cone drill bits have been proposed through the years to drill bore holes for mining, oil and gas exploration, and utility construction. It has been previously recognized that a single cone bit would offer superior design characteristics, such as bearing size permitting greater longitudinal compressive loading on the drill bit. A nutating single cone drill bit, for example the ones disclosed in U.S. Pat. No. 6,892,828 and PCT Pat. App. No. US2006/013540 entitled Drill Bit Lubrication Apparatus and Method, each incorporated by reference herein, can offer the advantage of long wearing cutter or crusher elements. Typically, traditional tri-cone bits must be repeatedly tripped out of the borehole due to excessively worn cutter elements.
A nutating single cone drill bit allows a longer service life, however these extended periods of downhole use can be limited by the amount of lubrication available to maintain the bearings of the nutating single cone drill bit. Without sufficient lubrication, the bearings can fail prior to the cutter, or crusher, elements of the bit requiring replacement, limiting the usefulness of the nutating single cone drill bit.